Grinding-mill



(No Model.)

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HWI ..f l' r 2 Sheets-Sheet 2. M. B. CHURCH.

GRINDING MILL.

Petented June 1,3, 1882.

PATENT l Finca.

MELVIN B. CHURCH, CF GRAND RAPIDS, MICHIGAN.

GRlNDlNG-IVIILL.

SPECIFICATION forming part of Letters Patent N o. 259,495, dated June13, 1882.

Application filed December 15, 1881.

To all whom it may concern:

Be itknown that I, M. B. CHURCH, of Grand Rapids, county of Kent, andState of Michigan, have invented a new and useful Improvement inGrinding-Mills; and I hereby declare that the following is a full, clearand exact description ofthe same.

My invention relates to grinding-mills of that class in which thematerial is ground between upper and lower stones.

The improvements relate more particularly to the form of the stones, andalso to their mode of operation, the invention consisting partly in themachine and partly in the art or mode of operating the machine. Icontemplate principally the grinding and regrinding of substances whichmay be reduced wholly to a very line dust or powdersuch as gypsum,chalk, earth-paints. ores, and the likethoughunder some circumstancesitmay be applicable to other goods.

The object of my invention is to avoid the great amount of frictionincidental to the old form of stones and great waste of power, theheating of the goods and the irregular grinding, by reason of whichanother expensive process is necessary-namely, that of boltingin orderto secure the necessary uniformity of neness which is required ofmaterials which are used for coating walls and for many'other purposes.

The millstones heretofore commonly used have, as is well known, furrowsapproximately radial in the grinding-faces ot' the upper and lowerstones, the effect of which is to act upon the materialground-technical1y called the food or goodsb-by a shearing action tocrowd such goods upon the lands, 7 where they are abraded by surfacesheld apart by the goods themselves, and also to regulate the outwardflow of the goods from eye to skirt. It is the crowding action of thesefurrows and the friction of the closely-set stones in the land portionswhich cause the great friction. The uneven distribution of air creates atendency to heat, and the grooves cause a discharge of a part of thematerial coarser than the rest, which interferes with the uniformity ofthe grinding and makes subsequent bolting necessary.

The essential principle of my invention lies (No model.)

in grinding between substantially smooth surfaces of stones with theunder stone smooth and the upper dished and slightly separated in aspace kept uniformly and constantly crowded full, whereby the goods arecaused mainly to grind by attrition and crushing ot' particle withparticle of their own substance. In order to accomplish this I havefound, by long study and experiment, that certain forms and conditionsof the stones are essential and effective. The approximate form ofstones is shown in the accompanying drawings, in which- Figure lrepresents a section 'taken vertically through 4the stones. Fig. 2 showsthe face of the stones. Fig. 3 shows in the upper part the adjusting andregulating devices for the feed, and in the lower ordinary devices fordriving the lower stone and for adjusting the stones. The devices shownin this last ligure are not new in this application, and thereforerequire only general reference. The upper part of the gure shows myimproved 'devices for adjusting the feed to the condition ofthe stoneshereinafter particularly referred to, and the lower part representsordinary devices for driving the lower stone, and for adjusting therelative position of the stones. In these figures the lower stone, A,which must always be the moving stone, is made with a perfectly plainlevel surface-from eye to skirt, which surface is either perfectlysmooth or formed with a very ne shallow cracking, for the purpose ofhelping the stones to stick to the vgoods and whirl them about andprevent them from packing down on the stones. The upper stone, B,isformed very slightly dishing from eye to skirt, and the surface of itmay be Vcracked in a manner similar to the lower. I

have said that the upper stone is dished very slightly and uniformlyfrom the eye to the skirt. It is better in practice to form a slightpocket immediately'about the eye suiicient in size to admit the granulesof the material to be ground full between the upper and lower stoneswhen they are in position for work. Ordinarily, as for regrindingplaster, I dish the upper stone about one-eighth of an inch at the eye,gradually lessening in not more than two inches toward the skirt toone-sixteenth of an inch, and from that line the dish grad- IOO uallydecreases to the skirt. These dimensions air is furnished uniformly overthe whole surare for a stone of thirty-six inches indiameter. Thesestones are provided with suitable mechanisms for feeding the materialuniformly thereto, for giving rotary motion to the lower stone, and forbringing the stones together. 1t is also essential, as will hereinafterappear, that the feed should be perfectly adjustable to the stones, andshould be automatically varied to suit the variations of the speed ofthe stones when runnin g. I prefer to accomplish this by means of theapparatus shown in application tiled by me in the United States PatentOffice on the 7th day of October, 1881, in which the feeding apparatusis regulated or adj usted by means of cone-pulleys to any requiredspeed, and is varied in its movements with the variations in the speedof the stones by connecting the feed mechanism with the power which'drives the stones. By means of this apparatus the feed can be regulatedto the stones, and afterward all the variations are automatic.

It will be understood from the statement heretofore given as to theconditions requirednamely, that the material shall be caused to crush orgrind itself mainly against its own substance, and crush and grind itswhole substance to acondition of uniform neness--that all the parts ofthe space between the stones must be filled and crowded with the goods.If there be any place in any part of that space between the stones notthus filled, there will be no action, or only imperfect action, aboutthat place. Vherever the goods lie upon the lower stone, and not inclose contact with the upper, no crushing or grinding will take place,since the stones run nowhere in contact. It follows, therefore, that thedish of the stone must be such that every part of the space will be keptfull. This is accomplished by exactly proportioning the dish, whichproportions have been given above; but the principle is that as thegoods moveoutward theywill have the same space (decreased in depth inproportion to the increase in length) in zones of a given width at everypoint from center to skirt, for if the goods occupying a zone, say, oneinch in width at the distance of six inches from the eye, quite lillthat space, as they are whirled round and reach a space one foot fromthe eye, where v the Zone of an inch width would be muchlonger, theywould nd, if there were no dishing or too little dishing, much largerspace, and they would not be crowded. On the other hand, if the dishingwere too great they would be overcrowded and clog. Again, it isessential that the surface of the lower stone should be a perfectlyplain surface, since the goods rest upon that surface and are carriedoutward by the centrifugal action alone, which would be insufficient ifthis stone were dishing. With the stones as formed a speed of threehundred and fifty to four hundred revolutions per minute is required togive the proper motion to the goods. I have found that with thisconstruction there is no heating of the goods, as the face.

The mode of operation of these stones has been partially indicated inthe description of their form and movement. It may be further statedthat the goods must be Afed in quantity or amount exactly sufficient tokeep the space between the stones constantly crowded full and no more,and this must be done at all times and under all variations ot' thespeed of the stones. Then the feed is once estabn lished and adjusted tosatisfy these conditions the material is ground to any desired degree oftineness and of such perfect uniformity that no bolting is afterwardrequired; and, further, I have found by actual experiment that the millcan be run with about one-fourth the amount of power to grind the sameamount and class ot' goods, and there is the further saving in the costof dressing the stones.

In running these stones according to my iniproved method the operatorwill be able to adjust the feed and the stones by carefully observingtheir action and the condition of the material escaping from thedischarge-spout..-

supposing the mill to be provided with an automatic feed-regulator, suchas heretofore referred to, and the stones with the ordinary adjustingand driving mechanisms, the operator will start the feed, turning thespout aside and observing the discharge. If the stones have beensetproperlyandthefeed properlyadjusted, the discharge, after a slightdelay while the space is lling, will appear of a proper degree offineness and uniformity; but if, as may happen, especiallyif theoperator be inexperienced, the stones are not properly set at the start,he should gradually bring the stone up until the proper degree ofIineness and uniformity is attained. 1f before reaching that point hefind that the stones begin to clog in the eye and check the motion, hewill then understand that IOO the feed is too great forthat degree ofneness.

He will then'lessen the feed by means of the cone-pulleys or by anyother equivalent mechanism which may be used. vHaving reduced the feed,the operator will again proceed and raise the stone until he arrives atproper results, or will continue this method of adjustment until hefinds the feed properly regulated to the stone. This being once reachedcan be maintained for the same class of goods, but might have to bevaried for another class. It' the operator find that the stone clogs atthe eye without being checked, he'wi-ll understand that the feed is toogreat for the eye, or that the granules of the goods are too large forthe pocketl or dish immediately about the eye. To remedy this and to fitthe stone for such granules, the eye and the pocket immediately aboutthe eye must be increased, for it will be understood that in thisrespect the stones must be varied for different sizes of granules. Inregrindin g plaster thirty-sixinch stones with ve-horse power will grindone ton an hour finer than can be obtained with the nest flour- IIO IIS

IZO

bolt. If the stones should not appear to be performing their full amountof work, the operator should increase the feed, and, if necessary, readjust the stones until the desired results are obtained.

I am aware that stones have been made smooth with dishing in the upperand lower surfaces, but only part way from eye to skirt, and with theupper stone running for the purpose of scouring and hulling but notgrinding; also, that a smooth dress on the outer surface and furrowsabout the eye half-way to skirt with the upper stone running and with ablast to force the feedis not new; also, that a smooth dress is not newin connection with a lower stone in the form of the frustum of a conewhen the dischargeis obtained by gravity.

Having thus described my invention, what I claim as my invention is- 1.In a grinding-mill, a lower stone adapted to be driven and formed withits face perfectly plain from center to skirt, in combination with anupper stone, said stones having a substantially smooth dress, and theupper stone dished substantially from eye to skirt in the mannerdescribed, whereby the spaces between the stones in zones of a givenwidth on any part from center to skirt are'made of equal capacity, allas set forth.

2. The improvement in the art of grinding, which consists in feeding thematerial to be ground between the stones, the lower one revolving andhaving a plain face and the upper one having a dished face, the dishinggiving equal capacity to zones of equal width at different distancesfrom the center in adjusting and regulating the feed to the speed of thestone, keepingthem crowded full, in adjusting the speed of the stone toaccord with the pressure necessary to the degree ofineness required, andin discharging the nely and uniformly ground material by centrifugalforce, substantially as described.

1u testimony whereof I hereunto affix my signature in the presence oftwo subscribing witnesses.

MELVIN B. CHURCH. Witnesses:

F. L. MIDDLETON, E. A. DIK.

